Non-malignant asbestos pleural disease

Our plain-English summary of Non-malignant asbestos pleural disease, by G. Hillerdal (Thorax, 1981).

The study

• Author: G. Hillerdal
• Journal: Thorax
• Published: 1981;36(9):669-75
• Cited by: 78 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000748).

Abstract

During a 10-year period (1970-79) all patients in Uppsala County found to have pleural changes related to asbestos exposure were followed. The lesions could be divided into four types: parietal pleural plaques, exudative pleurisy, thickening of the visceral pleura, and progressive pleural fibrosis. There were 891 cases. The most common type was parietal plaques, which was seen in 827 patients, some of whom later developed other changes. In 22 types exudation was proven radiologically, and in 84 more cases obliteration of the costo-phrenic angle was seen. The exudations almost all had a benign course, despite sometimes fairly large and bloody effusions. They were practically all symptom-free, being a surprise finding on chest radiography. Thickening of the visceral pleura can only be seen radiologically in the fissures and occurred in a few cases in addition to other changes. In a small group of more heavily exposed individuals, a progressive pleural fibrosis developed, sometimes after an initial effusion.

In plain English

This article described a ten-year follow-up (1970-79) of all residents of Uppsala County, Sweden, found to have pleural changes thought to be caused by asbestos. Most were found on chest X-rays from a county health survey. The county had no dockyards or asbestos factories, and exposed people were mainly builders, plumbers and workers in small manufacturing shops. The author sorted the changes into four types. Of 891 people, 827 had parietal pleural plaques. By the end of 1979, at least 2.2% of men aged 40 or older were estimated to have plaques. Fluid around the lung (effusion) was proven in 22 patients and was often bloodstained. These patients typically had no or very slight symptoms. All had been followed for at least three years without signs of a tumour, and four developed progressive pleural fibrosis. Progressive pleural thickening occurred in 27 patients, whose average exposure grade was higher than in the other groups. The author concluded that most effusions ran an uncomplicated course, while noting that three years is a short period to exclude mesothelioma.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Descriptive follow-up of all patients with asbestos-related pleural changes in one county over 10 years (a case series), classified by chest X-ray appearance
• Who was studied: 891 residents of Uppsala County, Sweden (about 250,000 inhabitants) with pleural changes associated with asbestos exposure, 1970-79. Most were found through a general health survey with chest X-rays, and fewer than 5% were referred to the clinic.
• Exposure: Mostly relatively low-grade occupational asbestos exposure among builders, plumbers and small-scale manufacturing workers, with no dockyards or asbestos factories in the county. Exposure was graded 1 to 3 from each patient's history. Fiber types were not specified.
• Main results:
  • Parietal pleural plaques were the most common change, seen in 827 patients. Some of them later developed other types of change as well.
  • By the end of 1979, at least 2.2% of men aged 40 or older in the county were estimated to have pleural plaques on X-ray. Plaques were very rare in women and in people under 40.
  • Among patients with plaques, more than 90% were asked about asbestos exposure, and 80% of those asked confirmed it. In another 10%, exposure was probable from their occupation.
  • For patients with plaques, the average time from first exposure to the first X-ray meeting the criteria was 30 years.
  • Pleural effusion was proven in 22 patients. The fluid was often visibly bloodstained.
  • In the 22 effusion patients, there were typically no or very slight symptoms. Only one had a chest X-ray because of symptoms.
  • Fluid tests and pleural biopsy sometimes raised suspicion of a tumour, but all effusion patients had been followed for at least three years with no signs of a tumour.
  • In effusion patients, the average exposure grade was 1.3. The mean time since first exposure was about 30 years, ranging from 9 to 46 years.
  • In 84 further cases, the angle at the base of the lung (costophrenic angle) was obliterated without a known episode of effusion. Their average latency was 34 years and their average exposure grade was 1.4.
  • Thickening of the visceral pleura was not very common and tended to occur with comparatively heavy exposure.
  • Progressive pleural thickening occurred in 27 patients and was always bilateral. In four of them it started with an effusion.
  • In the progressive pleural thickening group, latency was 34 years and the average exposure grade was 2.0, higher than in the other groups.
  • Four patients with progressive pleural fibrosis had pleurectomy (surgical removal of pleura). Only one had subjective improvement in breathlessness. The author attributed the lack of improvement to coexisting pulmonary fibrosis proven by lung biopsy.
  • Six patients developed a 'pseudotumour': three after effusion and three with progressive thickening. At operation, these proved to be visceral pleural thickening and 'folded lung', not tumours.
• The authors' conclusion: The author concluded that, in this series, most asbestos-related effusions ran an uncomplicated course without signs of lung disease, and that the effusions diagnosed are only the 'top of the iceberg'.
• Limitations the authors state:
  • Three years of observation, as in some effusion cases, is a short period to exclude mesothelioma.
  • Visceral pleural thickening was not systematically looked for until the last few years of the study.
  • In some effusion cases, plaques may have developed later but been hidden by remnants of the pleurisy.
  • Asbestos exposure was not required for a plaque diagnosis because exposure can be very difficult to ascertain.
  • Only clinically motivated investigations were performed.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis, Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: Asbestos-Related Pleural Disease, Asbestos Exposure, Pleural Plaques, Pleurisy, Visceral Pleura, Fibrosis.

Related studies

• Asbestos: when the dust settles an imaging review of asbestos-related disease — H.D. Roach, G.J. Davies, et al. (2002)
• Pleural disease during treatment with bromocriptine in patients previously exposed to asbestos — G. Hillerdal, J. Lee, et al. (1997)
• CT and MR in pleural disease — T.C. McLoud (1998)
• The additional risk of malignant mesothelioma in former workers and residents of Wittenoom with benign pleural disease or asbestosis — A. Reid, N. de Klerk, et al. (2005)
• Chest pain in asbestos-exposed individuals with benign pleural and parenchymal disease — S. Mukherjee, N. de Klerk, et al. (2000)
• Computed tomography features in malignant pleural mesothelioma and other commonly seen pleural diseases — M. Metintas, I. Ucgun, et al. (2002)

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